Compressors, in the same way as turbines in axial turbomachines, for example, aircraft engines, typically include a rotor having a plurality of rotor blade rows, that are connected to a rotor shaft, and a stator in which the rotor rotates about the central axis thereof. The stator is essentially composed of a casing and of a plurality of guide vane rows. Configured between the rotor and the stator is a flow channel through which a primary flow traverses the turbomachine. The guide vane rows are adapted for suitably directing the primary flow to the rotor blade rows. The rotor blades of the rotor blade rows can be individually manufactured and inserted into slots of a mounting portion, in particular into grooves of a rotor disk; or one-piece blisks (bladed disks) can be used which each include a disk, a ring and/or a drum portion having a plurality of rotor blades integrally formed thereon or joined (for example, welded) thereto in one piece. As compared to rotor blade rows composed of individual blades, such blisks have the particular advantage of a greater mechanical strength and a lower weight.
To prevent losses, it is necessary, in particular, that passages formed between movable and fixed components be kept as small as possible. For instance, what are generally referred to as “sealing fins” are known for sealing such passages between the rotor and the radially inner tips of the guide vanes. These are generally each formed as annular, radial projections and adapted for engaging by a tip portion into abradable coatings provided on the guide vane tips. Unless otherwise stated, the specification “radial,” as well as “axial” always refer here to the intended axis of rotation of the rotor or of a rotor shaft.
To ensure that the sealing fins are able to resist the mechanical and thermal stresses that occur upon engagement into the abradable coatings, the tip and side portions thereof are generally coated. However, selective coating requires that side portions of the tip be accessible to the respective coating tool. Therefore, when working with one-piece blisks, a closely positioned rotor blade row or another, proximate sealing fin can make it impossible or, at the least, very difficult to apply a coating from an axial direction. Therefore, to simplify the radial coating of a tip portion of a blisk sealing fin, the German Patent Application DE 10 2009 055 913 A1 discusses shaping the flanks of the tip portion to be flatter than the flanks of a radially inner sealing fin portion. In general, this difficulty can arise even when working with rotor disks having a mounting portion for the rotor blades of a rotor blade row, particularly when the mounting portion ends radially outwardly relative to the sealing fins.